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Vitamin D in high doses may increase risk of asthma

Published Online: February 1, 2015

Allergic disease is one of the most common chronic conditions worldwide. Symptoms usually develop early in childhood, which suggests that early life exposures may influence the risk of developing allergic disease. Low levels of vitamin D during pregnancy has been identified as a potential risk factor for developing allergic disease in the child but findings from previous studies have been conflicting. Furthermore, it is not known whether low levels of vitamin D in pregnancy has the potential to influence the risk of allergy development past childhood. Now, in a study recently published in The Journal of Allergy and Clinical Immunology (JACI), S. Hansen and colleagues present the first results from a long-term follow-up of Danish adults whose mothers participated in a study when they were pregnant.

In 1988-1989, 965 pregnant women were enrolled in the study and gave a blood sample, which was used to measure levels of vitamin D. The children were tracked from their birth until the end of 2013, when they were around ~25 years of age, in Danish population-based disease registries by using the unique personal identification number given to all Danish citizens. We obtained information about the children’s use of asthma medication and allergic rhinitis medication, and their hospitalizations due to asthma during the follow-up period. Furthermore, around 50% of the children participated in a clinical examination in 2008, when they were ~20 years old, where they had a blood sample drawn and their lung function was measured.

The authors found no evidence that high vitamin D levels (>125 nmol/L) in pregnancy protected against allergic disease in the child. In contrast, those children whose mothers had high levels of vitamin D had an increased risk of having been hospitalized for asthma compared to children of mothers who had recommended levels of vitamin D (75-125 nmol/L). There was furthermore a lower risk of using asthma medication and of asthma hospitalizations among children whose mothers had low vitamin D levels in pregnancy (<50 nmol). The authors did not see any association between vitamin D levels in pregnancy on lung function or allergic rhinitis.

Therefore, this study does not support high dose vitamin D supplementation to pregnant women with the purpose of preventing allergic disease in their children. Results from intervention studies are on their way and will hopefully provide further information on the role of vitamin D in pregnancy and allergic disease.

The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.